Wood finishing process



OGL 30, 1951 D.v P. LEHMAN v 2,573,105

WOOD FINISHING PROCESS Filed Jan. 27, 1948 I N VEN TOR.

Patented Oct. 30, 1951 UNITED lSTATES PATENT OFFICE WOOD FINISHING PROCESS David P. Lehman, Elkhart, Ind. Application January 27, 1948, Serial No. 4,560

4 Claims. l

This invention is concerned with an improved method of treating the surface of ring porous woods to provide thereon a protective finish.

In the conventional treatment of Wood surfaces to provide a finish which is lighter in shade than the woods own natural color various bleaching methods are practiced. Such methods involve the treatment of the wood surface with caustic bleach materials, such as 100 volume peroxide. In practicing such methods several successive coats of the bleaching agent are applied vand considerable time is required for the necessary chemical reaction of the bleaching agent with the coloring agents in the wood, and for drying, sanding, etc. between coats. Also, numerous bleaching materials involve re and health hazards which require rather elaborate precautions inthe use of the materials. The results obtained by such methods are frequently unsatisfactory. The effect of the bleaching materials Varies to a considerable extent, uniform results are diicult of achievement, and the nal finish cannot be depended upon t remain permanent over the long periods of time desirable for the finish on furniture and similar products.

It is a general object of the invention to provide a simple and effective method of finishing ring porous woods such as oak, ash, mahogany, walnut, etc. without the use of causigc bleaching materials or the like to produce a permanent and durable finish in light or blond shades.

It is another object of the invention to provide an improved method of flnishing ring porous woods to provide on the surface thereof a permanent and durable finish in shades lighter than the natural color of the wood which simulates the nish heretofore produced by various bleaching processes.

It is a further object of the invention to provide a method of finishing ring porous woods to obtain blond or pastel shades lighter than the woods own natural color without the use of any caustic bleaches and by means of a series of steps which may be practiced in a much shorter time than heretofore required to obtain similar shades by bleaching methods.

A more specific object of the invention is to provide a method of finishing ring porous woods wherein a very thin coat of pigmented primer material is sprayed at an extremely low angle approaching a position parallel to the surface of the wood whereby the relatively solid areas between the open pores of the wood surface are coated with the pigmented finishing material and thereafter :filling the pores with a. silex filler or the like and finally finishing the surface with transparent lacquers or similar material.

These and other objects of the invention will be apparent to those skilled in the art from a consideration of the steps illustrating the method which are described herewith, reference being had to the accompanying drawings, wherein:

Fig. 1 is a plan view of a section of board finished in accordance with a method which embodies the principles of the invention;

Fig. 2 is a sectional view, taken on the line 2 2 of Fig. 1, to an enlarged scale with thick.- nesses of material greatly exaggerated;

Fig. 3 is a section similar to Fig. 2 prior to the application of the finishing materials;

Fig. 4 is a section similar to Fig. 2 after the application of the initial, pigmented primer material;

Fig. 5 is a perspective view illustrating the application of the pigmented primer material to a section of board; and

Fig. 6 is a section taken on the line 6-6 of Fig. 5.

Ring porous woods such as oak, ash, mahogany. walnut, etc. which are adapted to be finished by the improved method of this invention provide a surface when cut into boards or Veneer sheets which is characterized by relatively small depressions or recesses, constituting the pores of the wood, separated by relatively solid appearing areas or portions. The solid appearing portions actually contain a large number of much finer pores of varying degrees of size and depth, many of which are scarcely visible to the naked eye. The pores which are clearly visible are somewhat greater in size and depth. In such woods the grain pattern formed by the distribution and arrangement of the pores is distinctive, and in finishing processes one of the objectives usually sought is to retain the pleasing appearance of the surface which is due to the grain pattern. Various means are used to emphasize or bring out the pattern of the grain of the wood in the Various finishing processes.

Certain of the ring porous woods such as mahogany have a distinctive color which changes and becomes darker as the wood ages. Mahoganies from different wood producing areas of the world vary considerably in color when they are freshly cut and surface and initially exposed to the light. The color producing elements in the wood are affected by the light and gradually change the color to a darker shade. Other porous grain woods are lacking in uniformity of color. Some boards will show considerablevariation of color over a relatively small area while separate boards cut from different sections of the same tree or from different trees show considerable variation in overall appearance. The

.- lack of uniformity in color and tendency to darken with age present obstacles to be overcome when it is desired to provide on such woods a finish of a uniform color which is lighter than the natural color of the wood. Such finishes are customarily obtained in either one of two ways. wood surface may be covered or painted with a pigment of the desired shade. This method of finishing obscures the grain pattern of the wood due to the fact that the pigment settles into the finer pores and completely fills them so that they lose their identity and the iinal nish lacks the beauty contributed by the natural grain pattern. Efforts to obtain a painted finish which will have the beauty of the normal grain of the wood have been unsuccessful. Even the casual observer is almost immediately aware that the wood has been painted, while the person familiar with ne woods of this type is unable to even identify the wood without removing a portion of the finish.

The various processes developed for finishing wood surfaces of this type which rely on bleaching out the natural color of the wood without affecting the grain structure and obtaining a surface of uniformly lighter color than the natural color of the wood while retaining the grain pattern will successfully provide blond or pastel shades, but the disadvantages in the use of the bleaching materials are numerous. In most instances they must be applied in several successive coats in order to obtain a light colored uniform surface, and a considerable lapse of time between coats is required for the chemicals to react with the color producing elements in the wood. The use of many of the bleaching chemicals is hazardous from the standpoint of the health of the user and, because they are high oxidizing agents, precautions must be taken against re. The precautions necessary in the use of `the bleaching materials, the large number of preliminary opera.- tions and the lapse of time involved .greatly increase the cost of finishing the wood surface.

The improv-ed method of finishing .of this invention eliminates the use of bleaching chemicals and the costly operations which they involve while obtaining a rugged and durable finish which closely simulates the `finish obtained by the bleaching processes. y

Referring to the drawings, the first step in the method of the invention comprises subjecting the surface of the Wood it to a blast .of air or to a brushing operation to remove from the l pores Il the accumulation of dirt and dust deposited there by the preliminary operations of planing and sanding so that the pores `l l are empty and open at the top (Fig. 3). The surface of the wood then consists of the open topped DOT-.esti separated at the plane .of the surface :of 'the 'wood by substantially solid :areas pr .sectiQns @I2 in which the pores are not visible.

After the surface of the wood has .been cleaned a coating of pigmented primer material lrS is applied by a spray gun i4 as illustrated in Figs 5 and 6. The primer material must be high hiding. By high hiding is meant la material that will cover the .wood surface .to be coated, so as to change the surface to the ,color of the material, with very little material consumed.

The material must be of low solid contentJ iquick drying :and of such a character fthatitwill pro- The 4 duce an extremely tough and durable coating on the solid areas or sections I2`of the wood surface. A suitable primer material consists of the coating composition described in Patent No. 2,293,558 issued August 18, 1942, to Ray L. Overholt to which there has been added approximately of a suitable pigment. The material must be capable of being sprayed on the Wood surface to provide thereon a very thin coat which is highly scratch resistant, whichwill adhere to the surface of the wood and which will coat the solid wood portions of the surface without bridging over or covering up the wood pores which are of appreciable size. The material must be capable of being applied with substantially no filling of the visible pores I l.

The pigmented primer coating i3 (Fig. 4) is applied by a spraying operation, preferably across the grain of the wood, using a relatively high air pressure and at an extremely low angle approaching parallelism with the SllraCe being @Gated- A sufficient amount of the primer material is applied in this manner to form a very thin coat. The angle of application is critical and must be kept as low as possible in order to avoid lling to any appreciable extent the very small pores which are visible on ,the suriace of the material and thereby retain in the final finish as much detail of the visible grain pattern of the wood es possible. When the primer material I3 is applied in this manner the solid arcas l2 o f the surface of the wood are covered with a v ery thin coating of the material i3 and the pores l l remain open at the top for the reception of the filler material l5 (Fig. 2).

The open pores Ii are then filled. preferably by a silex base filler or any similar type of Ifiller' which will emphasize or bring out the natural .grain pattern in .the usual manner, The filler l5 will preferably be neutral in color or tinted if desired. y

.after the application of the ,llei l5 the nlShf ing process is completed ip the conventional Ymanner withnish ,coats of sealer I6 (Eigs. 1 and 2) and any desired number 0f @eats 0f lacquer o r 4varnish il.A sealer coat l5 and Afinal lacquer or varnish ccats il will be substantially .transparent so that the grain pattern is visible thro-ugh the same.

The finished surface (Figs. 1 2) is uniform in appearance and the natural pattern of the `wood grain is substantially retained. The .rie-

tural ybeauty of the grain pattern of the -vood is not destroyed but is retained .without appreciable change. The pores of the wood which are so tiny as to be hardly distinguishable with the naked eye are l not obscured by :the process .but

contribute to the final visible pattern .of .the finished surface. The surface is uniform in color and may be as" light as desired depending upon the pigment used in the priming coat. The steps involved in vcarrying out the method are simple and very little `skill is required. When .quick drying materials are usada wood surface may be finished in accordance with the teachings .of this method in a matter -of hours while several days time .are requiredfor finishing a like surface by bleaching methods.

It yizvill .be understood that the particular lmaterials and steps .of the method .described herein are .lto ibe taken .as illustrative .only Aand that -Variations are contemplated within ,the scope of the invention-as 4set out .in the claims. Y

.I vclaim: l

.Amethod offlnishine asubstantiallysmcoth ring porous Wood surface which comprises cleaning the pores of the surface to remove any loose material deposited therein and provide a sub-v stantially smooth surface having open topped visible pores separated at the plane of the surface by substantially solid areas, applying a liquid pigmented primer finishing material in a very thin film over the solid areas between the open pores of the surface by spraying the material at an extremely low angle approaching parallelism to the surface of the wood, said finishing material having a low solid content and being capable of adhering to the solid areas in a very thin lm but being incapable of bridging the visible pores whereby substantially no filling of the visible pores occurs, filling the open pores of the wood with a filler material which will emphasize the grain, and applying a film of transparent protective coating material thereover.

2. A method of treating a substantially smooth Wood surface which includes the steps of cleaning the pores of a ring porous Wood to remove loose material therein, spraying thereon at an extremely low angle approaching parallelism to the surface of the wood a liquid primer material of high hiding characteristics and low solid pigment content to coat the surface between the open tops of the pores Without covering the pores which form the visible grain pattern, said primer material having sufficient pigment content to change the color of the Wood to a bleached effect and still allow the grain to show, thereafter applying a filler material to the surface and removing the same from the portions of the surface coated by said primer material whereby to ll the uncovered pores with said filler material and thereby emphasize the grain pattern, and finally applying one or more coats of a transparent protective coating material thereover.

3. In a method of finishing the substantially smooth surface of a ring porous wood wherein open pores forming a visible grain pattern are separated by relatively dense wood areas, the improvement which consists of spraying at an extremely low angle approacing parallelism to the surface of the wood a relatively quick drying liquid primer iinish coat which is characterized by its ability to form a relatively thin covering iilm over the dense Wood areas between the open press without covering the pores which form the visible grain pattern and which is further characterized by a relatively low solid content with sucient pigment to change the color of the Wood to a bleached effect and still allow the grain to show.

4. A method of finishing a substantially smooth ring porous wood surface which comprises cleaning the pores of the surface to remove any loose material deposited therein and provide a substantially smooth surface having open topped visible pores separated at the plane of the surface by substantially solid areas in which the pores are not visible, applying a relatively quick drying liquid finishing primer material of low solid content over the solid areas between the open pores of the surface by spraying the material at an acute angle approaching parallelism to the surface of the wood, said finishing material being capable of adhering to the solid areas in a very thin film with substantially no filling of the visible pores and having suflicient pigment content to change the color of the wood to a bleached eiect and still allow the grain to show, filling the open pores of the Wood with a filler material to emphasize the grain, and applying a film of transparent coating material thereover.

DAVID P. LEHMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,345,610 Lehman Apr. 4, 1944 2,345,940 Lehman Apr. 4, 1944 2,345,942 Lehman Apr. 4, 1944 OTHER REFERENCES VanderWalker-Wood Finishing 1944, F. J. Drake & Co. Chicago, page 131. 

